The primary objectives are to assess the magnitude of extacellular human neutrophil elastase (NE) ingibitory activity in bronchoalveolar lavage (BAL) fluid following 14 days of oral DMP 777 administration twice daily or three times daily in adult patients with cystic fibrosis (CF) and to correlate this effect with any observed changes in extracellualar HNE activity in BAL fluid with systmeic pharmacokinetic (PK) and pharmacodynamic (PD) data. Evaluate the safety of DMP 777. The secondary objective is to determine the correlation between the magnitude of BAL extracellular HNE inhibition and improvement in biological indices relevant to the pathogenesis of lung disease in CF.